From 65b699979d2f02e16e30650e8f4d85d17d1553ae Mon Sep 17 00:00:00 2001
From: OSjoerdWie <github@difoga.nl>
Date: Tue, 16 Jun 2026 20:34:00 +0200
Subject: [PATCH] Ensure more greedy cell name replacement for defined names
 (NO1_VARIABLE should not become NO2_VARIABLE or NP1_VARIABLE)

---
 src/xlsx/mod.rs | 60 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)

diff --git a/src/xlsx/mod.rs b/src/xlsx/mod.rs
index 28e70cb8..d39dc378 100644
--- a/src/xlsx/mod.rs
+++ b/src/xlsx/mod.rs
@@ -3460,7 +3460,7 @@ fn expand_shared_formula_with_offset_into(
     let mut token_end = 0;
 
     for (i, &c) in bytes.iter().enumerate() {
-        if !in_quote && (c.is_ascii_alphanumeric() || c == b'$' || c == b':') {
+        if !in_quote && (c.is_ascii_alphanumeric() || c == b'_' || c == b'$' || c == b':') {
             token_end = i + 1;
         } else {
             if token_start < token_end {
@@ -4616,6 +4616,64 @@ mod tests {
             "한글 B1 テスト".to_owned()
         );
 
+        assert_eq!(
+            replace_cell_names("ABS(AND(Q1934;AA1_SOMETHING))", (0, 1)).unwrap(),
+            "ABS(AND(R1934;AA1_SOMETHING))".to_owned()
+        );
+
+        assert_eq!(
+            replace_cell_names("ABS(AND(Q1934;AA1_SOMETHING))", (1, 0)).unwrap(),
+            "ABS(AND(Q1935;AA1_SOMETHING))".to_owned()
+        );
+
+        assert_eq!(
+            replace_cell_names("Z1+1", (0, 1)).unwrap(),
+            "AA1+1".to_owned()
+        );
+
+        assert_eq!(
+            replace_cell_names("Z9+3", (1, 0)).unwrap(),
+            "Z10+3".to_owned()
+        );
+
+        assert_eq!(
+            replace_cell_names("Z1+A3B", (0, 1)).unwrap(),
+            "AA1+A3B".to_owned()
+        );
+
+        assert_eq!(
+            replace_cell_names("Z1+A3B", (1, 0)).unwrap(),
+            "Z2+A3B".to_owned()
+        );
+
+        // Named range after a cell ref.
+        assert_eq!(
+            replace_cell_names("A6+NO1_VARIABLE", (0, 1)).unwrap(),
+            "B6+NO1_VARIABLE"
+        );
+        assert_eq!(
+            replace_cell_names("A6+NO1_VARIABLE", (1, 0)).unwrap(),
+            "A7+NO1_VARIABLE"
+        );
+
+        // Named range before a cell ref.
+        assert_eq!(
+            replace_cell_names("NO1_VARIABLE+Q5", (0, 1)).unwrap(),
+            "NO1_VARIABLE+R5"
+        );
+
+        // Leading underscore named range — should pass through.
+        assert_eq!(
+            replace_cell_names("_PRIVATE+A1", (0, 1)).unwrap(),
+            "_PRIVATE+B1"
+        );
+
+        // Named range with multiple underscores.
+        assert_eq!(
+            replace_cell_names("NO1__DOUBLE+A1", (0, 1)).unwrap(),
+            "NO1__DOUBLE+B1"
+        );
+
         assert_eq!(
             replace_cell_names("ABC\"asd\"123", (1, 0)).unwrap(),
             "ABC\"asd\"123".to_owned()